1. Field of the Invention
The present invention relates to a support structure for supporting a foamable material on a hollow structural member, and more particularly to a support structure for supporting a foamable material in a cavity of a closed box-like hollow structural member constituted of a plurality of pieces of plates, such as pillars, rocker panels, roof side panels and hood panels of a vehicle body, in order that the foamable material blocks the cavity of the hollow structural member to increase damping powers, sound insulation powers and other powers of the hollow structural member when it is foamed by external heating.
2. Description of the Prior Art
FIGS. 9 and 10 exemplarily show a conventional support structure. In this support structure, to support a foamable material 121 in a cavity 106 of a closed box-like hollow structural member 101 which is constituted of an inner pillar panel 102 and an outer pillar panel 104, a bolt 111 having a threaded section 111a is mounted on the inner pillar panel 102 so that the threaded section 111a projects into the cavity 106 at a desired length. The threaded section 111a is then provided with a washer 120. The foamable material 121 engages the threaded section 111a so as to be seated on the washer 120. Thus, the foamable material 121 is supported in a cavity 106 of the hollow structural member 101.
Such a support structure of the foamable material as described above is disclosed, for example, in Japanese Laid-Open Patent Publication No. 2-276836 (corresponding to British Patent Application No. 8903211.4).
In the above-noted conventional support structure of the foamable material in which the foamable material 121 engages the threaded section 111a of the bolt 111 which projects into the cavity 106 of the hollow structural member 101, the foamable material 121 biases the inner surfaces of the inner and outer panels 102 and 104 and adheres thereto when it is foamed and expanded by external heating, thereby blocking the cavity 106 of the hollow structural member 101.
As shown in FIG. 10, the foamable material 121, when heated by external heating, is foamed and expanded to form a foamed product 122. The foamed product 122, when cooled, is contracted at an inherent contraction rate, thereby generating a contraction force. Such a contraction force causes formation of an uneven surface or distortional surface 126 on a corresponding outer surface area 108 of the outer panel 104 to which the foamed product 122 is bonded.
Particularly, in a case that the outer surface of the outer panel 104 is used as an open or exposed surface, the hollow structural member 101 may have undesirable awkward appearance resulting from such distortional surface 126.